Heat exchanger

ABSTRACT

A heat exchanger is provided. The heat exchanger includes a plurality of stacked layers of fins, each fin including a repeated pattern of folds, the plurality of stacked layers of fins forming a plurality of repeating offset cell structures and a first coolant duct and a second coolant duct coupled to peripheral fins in the plurality of stacked layers of fins. The heat exchanger further includes a fan directing air through the repeating offset cell structures.

FIELD

The present disclosure relates to a heat exchanger and method for operation of a heat exchanger.

BACKGROUND AND SUMMARY

Heat exchanger designs, such as automotive heat exchangers, may utilize rolled and/or folded fins to transfer heat to the air from a coolant or fluid that passes internally through a series of coolant tubes. Heat is conducted from the tubes to the fins where the fins physically contact the coolant tubes. U.S. 2012/0273182 discloses a heat exchanger having a fin member repeatedly extending between pipes in a corrugated folding pattern. The fin member removes heat from the pipes and discharges it into the air flowing through the fin.

The inventors have recognized several drawbacks with the heat exchanger disclosed in U.S. 2012/0273182. For instance, due to the uniformity of the fin design a small amount of turbulence may be generated in the air flowing through the fins. Decreasing turbulence decreases the heat transfer capability of the heat exchanger. Additionally, the small contacted area between the fins and the pipes further decreases the heat transfer capability of the heat exchanger. Consequently, the size of the heat exchanger may be increased to provide a desired amount of cooling.

The inventors herein have recognized the above issues and developed a heat exchanger. The heat exchanger includes a plurality of stacked layers of fins, each fin including a repeated pattern of folds, the plurality of stacked layers of fins forming a plurality of repeating offset cell structures. The heat exchanger further includes a first coolant duct and a second coolant duct coupled to peripheral fins in the plurality of stacked layers of fins. The heat exchanger further includes a fan directing air through the repeating offset cell structures.

The flow pattern generated by the offset cell structures increases turbulence in the airflow through the stacked layers of fins without increasing airflow losses through the cell structure beyond a desirable value. As a result, the heat transfer capability of the heat exchanger is increased. Specifically, in one example the repeating offset cell structures are configured to generate isotropically turbulent airflow through the fins. It will be appreciated that isotropically turbulent airflow further increases the amount of heat transferred to the air from the fins. Additionally, when the heat transfer capacity of a heat exchanger is increased the size of the heat exchanger may be decreased while achieving a heat transfer capacity of a larger less efficient heat exchanger. As a result, the compactness of the cooling system may be increased or the heat exchanger may provide increased cooling.

Additionally in one example, a plurality of planar surfaces of the peripheral fins may be coupled to the first and second coolant ducts. In this way, the size of the contact regions between the fins and the coolant ducts is increased, further increasing the heat transfer capability of the heat exchanger.

The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventors herein, and are not admitted to be known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic depiction of a vehicle system including an engine and a heat exchanger;

FIG. 2 shows an example heat exchanger;

FIG. 3 shows a portion of a fin structure in the heat exchanger shown in FIG. 2;

FIG. 4 shows a fin in the fin structure shown in FIG. 3;

FIG. 5 shows another example heat exchanger;

FIG. 6 shows the heat exchanger illustrated in FIG. 5 without one of the coolant ducts;

FIG. 7 shows a portion of a fin structure in the heat exchanger shown in FIGS. 5 and 6;

FIG. 8 shows a fin in the fin structure shown in FIG. 7;

FIG. 9 shows another heat exchanger;

FIG. 10 shows the heat exchanger illustration in FIG. 9 without one of the coolant ducts;

FIG. 11 shows a detailed view of a portion of the fin structure shown in FIGS. 9 and 10;

FIG. 12 shows a view of layers of fins included in the fin structure shown in FIG. 3;

FIG. 13 shows an example pyramid type structure; and

FIG. 14 shows a method for operation of a heat exchanger.

DETAILED DESCRIPTION

A heat exchanger having a plurality of stacked layers of fins forming a plurality of repeating offset cell structures is described herein. Peripheral fins in the plurality of stacked layers of fins are coupled to a first and second coolant duct. The offset cellular fin design offers a number of performance enhancements over previous designs such as increasing heat transfer from the fins to the air via increased turbulence (e.g., isotropic turbulence) generation and increased fin surface area. Specifically, the offset cells generate a desired amount of airflow turbulence within the heat exchanger without increasing the pressure drop in airflow across the heat exchanger above a desirable level. In this way, the heat rejection capacity of the heat exchanger is increased. Moreover, the offset cellular fin design is also less susceptible flow disruption caused by fin deformation (e.g., crushing), cell obstruction, and other types of degradation of the fins due to the large number of interconnected flow paths in the cell structures, providing alternate flow paths around the damaged/obstructed regions.

Additionally, in some examples planar surfaces in the peripheral fins may be in face sharing contact with surfaces of the coolant ducts. Consequently, heat conduction from the coolant ducts (e.g., coolant tubes) to the fins is increased due to an increase of contact area between the tube and fins when compared to fins coupled to the tube via edges of the fins. The aforementioned benefits enable an increase in the heat rejection capacity of the heat exchanger. Consequently, the size and weight of the heat exchanger may be reduced or the heat rejection capacity of the heat exchanger may be increased.

FIG. 1 shows a schematic depiction of a vehicle system 10 including an engine 12 and a heat exchanger 50. The engine 12 is configured to implement combustion operation. For example, a four stroke combustion cycle may be implemented including an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. However, other types of combustion cycles may be utilized in other examples. It will be appreciated that heat is generated during combustion. Therefore, the heat exchanger 50 is configured to remove heat from the engine 12.

An intake sub-system 14 is included in the vehicle system 10 and configured to provide intake air to cylinders 16 in the engine 12, denoted via arrow 15. The vehicle system 10 further includes an exhaust sub-system 18 configured to receive exhaust gas from cylinders 16 in the engine 12, denoted via arrow 19. The engine 12 may be formed of a cylinder head 20 and a cylinder block 22.

One or more cooling passages 24 may traverse the cylinder head 20 and/or cylinder block 22. The cooling passages 24 are in fluidic communication with the heat exchanger 50, discussed in greater detail herein. However, in other examples the heat exchanger 50 maybe coupled to other suitable cooling systems in the vehicle such as a turbocharger cooling system.

A fan 30 is also included in the vehicle system 10. The fan 30 is configured to direct air to the heat exchanger 50, depicted via arrows 31. In this way, airflow may be generated by the fan to increase the cooling via the heat exchanger. However, in other examples the heat exchanger may be positioned at a location where airflow is generated from vehicle motion. A pump 32 is also included in the vehicle system 10. The pump 32 is coupled to the coolant passages 24 and configured to circulate coolant through the coolant passages 24.

The heat exchanger 50 is shown included in a vehicle cooling system in FIG. 1. However, it will be appreciated that the heat exchanger may be used in a variety of applications such as residential air conditioners, industrial systems, etc.

FIGS. 2-4 show a first example heat exchanger 200. The heat exchanger200 may be included in the vehicle system 10 shown in FIG. 1. Therefore, the heat exchanger 200, shown in FIGS. 2-4, may be the heat exchanger 50 schematically depicted in FIG. 1.

FIG. 2 shows a perspective view of the first example heat exchanger 200. The heat exchanger 200 includes a first coolant duct 202 spaced away from a second coolant duct 204. The first coolant duct 202 and the second coolant duct 204 each include a coolant inlet 206. Additionally, the first coolant duct 202 and the second coolant duct 204 each include a coolant outlet 208. The coolant inlets and outlets (206 and 208) may be in fluidic communication with cooling passages 24 shown in FIG. 1 or with other suitable coolant conduits, such as coolant conduits in a turbocharger system, coolant conduits in an exhaust gas recirculation (EGR) system, etc. Thus, a suitable coolant may flow through each of the first and second coolant ducts (202 and 204). The coolant inlets are positioned on the same side of the heat exchanger in the depicted example. However, in other examples, the coolants inlets may be positioned on opposing sides of the heat exchanger.

Continuing with FIG. 2, a fin structure 210 extending between the first coolant duct 202 and the second coolant duct 204 is also included in the heat exchanger 50. The fin structure 210 includes a plurality of fins 212. Peripheral fins in the fin structure 210 may be coupled to the first coolant duct 202 and the second coolant duct 204. Each of the fins may extend from the inlets 206 to the outlets 208 of the coolant ducts.

The direction extending from the inlets to the outlets is referred to as a longitudinal direction. The direction perpendicular to the longitudinal direction and extending between the first coolant duct 202 and the second coolant duct 204 is referred to as a transverse direction. A lateral direction, perpendicular to the longitudinal direction, extending from a first side of the coolant ducts to a second side of the coolant ducts is referred to as a lateral direction. A longitudinal axis, transverse axis, and a lateral axis are provided for reference.

It will be appreciated that the fan 30, shown in FIG. 1 may be configured to direct air through the fin structure 210. The airflow enables heat to be transferred from the heat exchanger to the surrounding air. The general direction of airflow from the fan may be perpendicular to the leading edge of the fin structure 210.

FIG. 3 shows an expanded view of a portion 300 of the fin structure 210 shown in FIG. 2. As previously discussed, the fin structure includes a plurality of fins 212. Additionally, each of the fins 212 is equivalent in size and shape to the other fins in the fin structure. However, a fin structure with fins having an unequal size and/or shape has been contemplated.

The fin structure forms a plurality of repeating offset cell structures 302. Offsetting the cell structures generates turbulence (e.g., isotropic turbulence) in the air flowing through the fin structure. Specifically, the fins of the cell structures may act as a flat plate airfoil, causing the entering flow to split on both sides of each of the fins. The splitting of the flow results in turbulence generation, which is enhanced as the flow progresses through the next layer of cells. Changing the relative direction of the incoming flow to the cell axis can further enhance turbulent generation as the flow will separate off the upper surface of each flat plate airfoil fin.

As previously discussed, the airflow may be generated via a fan and directed into the cell structures 302. It will be appreciated that the general direction of airflow at the leading edge of the fin structure is in a lateral direction. After the air travels past the leading edge of the fin structure, turbulent airflow may be generated. As shown, the cell structures 302 have a square cross-section, the cutting plane of the cross-section extending in a longitudinal and transverse direction. Again a longitudinal axis, a transverse axis, and a lateral axis are provided for reference. The cells may be divided into laterally aligned sets. Therefore, each of the cells in a set has a similar lateral position. Additionally, the sets of aligned cell structures are offset in a longitudinal and transverse direction. The cell structures 302 have square cross-sections. The cutting plane of the cross-sections is perpendicular to a lateral axis. However, cell structures having cross-sections with different geometries have been contemplated. For example, the cell structures may have a rectangular or triangular cross-section, in other examples. Furthermore, due to the offset between the cells structures cells in non-peripheral sections of the structure each flows air to four downstream cell structures and/or receives air from four upstream cell structures. In this way, a large number of flow paths are formed in the fin structure, thereby increasing turbulence in the fin structure as well as making it less susceptible to large drops in airflow through the cell structures caused by damaged fins and/or blocked cells.

The plurality of fins 212 may be divided into layers. The fins in each of the layers are sequentially stacked and aligned in a transverse direction and longitudinal direction. However, layers having other orientations have been contemplated. Specifically, a first layer of fins 310 and a second layer of fins 312 are shown in FIG. 3. The first and second layers of fins are offset in a longitudinal and transverse direction. It will be appreciated that each of the layers of the fins shown in FIG. 3 may include additional fins. Furthermore, each of the first layers of fins 310 and second layers of fins 312 extend between the first and the second coolant ducts (202 and 204), shown in FIG. 2. In this way, heat may be conducted from the coolant ducts to the fin structure.

Each of the fins in the first layer of fins 310 are aligned in a transverse direction. This alignment enables the cells (e.g., square cells) to be formed via the fin structure. Therefore, each of the layers form a plurality of cells. It will be appreciated that the first layer of fins 310 is offset from the second layer of fins 312.

Peripheral fins 304 are shown in FIG. 3. The corners 306 in the peripheral fins 304 may be coupled (e.g., braised) to a surface (e.g., peripheral surface) of the first coolant duct 202, shown in FIG. 2. Likewise, additional peripheral fins spaced away from the peripheral fins 304 may be coupled to a surface (e.g., peripheral surface) of the second coolant duct 204, shown in FIG. 2. The fins may be coupled to adjacent fins via braising and/or other suitable coupling techniques. For example, a portion of the fin structure may be cast, extruded, etc.

Additionally, each fin in the fin structure further includes laterally-peripheral edges. The laterally-peripheral edges 320 of fins in the first layer of fins 310 are in contact with laterally-peripheral edges 322 of fins in the second layer of fins 312. The edges (320 and 322) form perpendicular angles with one another. However, other angles have been contemplated. In this way, a large number of flow paths within the fin structure are created. As a result, increased turbulence (e.g., isotropic turbulence) may be generated in the air flowing through the fin structure during operation of the heat exchanger.

Additionally, when the sequential layers of fins are consecutively numbered, even numbered layers are transversely and longitudinally aligned. Likewise, odd numbered layers are transversely and longitudinally aligned and the even numbered layers are offset (e.g., longitudinally and transversely offset) from the odd numbered layers.

FIG. 12 shows another view of the first layer of fins 310 and the second layer of fins 312, shown in FIG. 3. The second layer of fins 312 is dashed to highlight the distinction between the layers. As shown, the first layer of fins 310 is offset by half the lateral width 350 of one of the cells included in the layer of fins from the second layer of fins 312. However, other degrees of offset have been contemplated. For example, the first layer of fins may be offset by a quarter of the lateral width of the cells from the second layer of fins.

FIG. 4 shows one of the fins 400 included in the fin structure 210 shown in FIGS. 2 and 3. As shown, the fin 400, depicted in FIG. 4, includes a plurality of consecutively arranged planar surfaces 402. All of the planar surfaces are equivalent in size and shape. However, in other example some of the planar surfaces may not be equivalent in size and/or shape.

An angle 402 is formed between consecutively arranged planar surfaces. The angle 402 is 90 degrees, in the depicted example. Therefore, the consecutively arranged planar surfaces are perpendicular to one another. However, other angles between consecutively arranged planar surfaces have been contemplated. Thus, the fin 400 includes a repeating pattern of folds.

The fin 400 may be formed from a continuous piece of material. Therefore, the fin 400 may be manufactured via extrusion, casting, etc. The fin 400 may be constructed out of a suitable material such as a metal (e.g., aluminum, steel, etc.). The width 452 of the fins may range from 2-3 mm. Further in another example the width 452 of the fins may be ≦10 mm. The widths of the fins may be selected based on the viscosity of the external cooling fluid (e.g., air or liquids). Further in some examples, a ratio between the width 452 and a length 454 of one of the planar surfaces may be between 1/1-1/10 or 1/15.

As shown the fin 400 defines a plurality of triangular air-flow channels 410. Each of the triangular air-flow channels 410 bounded by two consecutively arranged planar sides in the fin 400. It will be appreciated that when fin 400 is coupled to adjacent fins in a set of stacked fins, adjacent triangular air-flow channels form square air-flow channels.

FIGS. 5-8 show another example of a heat exchanger 500 that may be included in the vehicle system shown in FIG. 1. Thus, the heat exchanger 500 may be the heat exchanger 50, shown in FIG. 1, in some examples. Therefore, the heat exchanger 500 may receive a suitable coolant from the coolant passages 24 shown in FIG. 1 or coolant from another suitable system. Specifically, FIG. 5 shows a first coolant duct 502 spaced away from a second coolant duct 504. Both the first coolant duct and the second coolant duct include an inlet 506 and an outlet 508. The heat exchanger 500 also includes a fin structure 510 extending between the first and second coolant ducts (502 and 504). The fin structure 510 includes a plurality of fins 512. The fin structure 510 also extends between the inlets 506 and the outlets 508. However in other examples, the fin structure 510 may only partially extend between the inlets 506 and the outlets 508. A longitudinal axis, lateral axis, and transverse axis are provided for reference.

FIG. 6 shows the heat exchanger 500, shown in FIG. 5 without the first coolant duct 502. Peripheral fins 600 included in the fin structure 510 are shown in FIG. 6. It will be appreciated that planar surfaces 602 of the peripheral fins 600 may be coupled to a surface (e.g., peripheral surface) of the first coolant duct 502, shown in FIG. 5. Specifically, the planar surfaces 602 may be in face sharing contact with a surface (e.g., peripheral surface) of the first coolant duct 502, shown in FIG. 5. In this way, the contacted area between the fins and the coolant ducts is increased, thereby increasing the heat transfer capacity of the heat exchanger. Again the fin structure 510 includes a plurality of stacked layers forming a plurality of repeating offset cells structures, discussed in greater detail with regard to FIG. 7.

FIG. 7 shows a portion 700 of the fin structure 510 shown in FIGS. 5 and 6. The fin structure 510 includes a plurality of stacked layers of fins including a first layer of fins 710 and a second layer of fins 712 forming cell structures 702. The cell structures 702 have a square cross-section. The cutting plane for the cross-sections is perpendicular to a lateral axis. A longitudinal axis and a transverse axis are also provided for reference. Furthermore, due to the offset between the cells structures cells in non-peripheral sections of the structure each flows air to two downstream cell structures and/or receives air from two upstream cell structures. In this way, a large number of flow paths are formed in the fin structure, thereby increasing turbulence in the fin structure as well as making it less susceptible to large drops in airflow through the cell structures caused by damaged fins and/or blocked cells.

Additionally, each fin in the fin structure further includes laterally-peripheral edges. The laterally-peripheral edges 730 of fins in the first layer of fins 710 are in contact with laterally-peripheral edges 732 of fins in the second layer of fins 712. The edges (730 and 732) are parallel to one another. However, other orientations have been contemplated.

The first layer of fins 710 is offset by half the lateral width of one of the cells included in the layer of fins from the second layer of fins 712. However, other degrees of offset have been contemplated. For example, the first layer of fins may be offset by a quarter of the lateral width of the cells from the second layer of fins.

FIG. 8 shows a fin 800 included in the fin structure 510 shown in FIG. 7. The fin 800 includes a plurality of consecutively arranged planar surfaces 802. The fin 800 define a plurality of square air-flow channels 804 bounded by three consecutively arranged planar sides in the fin 800. It will be appreciated that when fin 800 is coupled with adjacent fins in a set of stacked fins, the square air-flow channels are bounded by four planar sides. An angle 806 is formed between consecutively arranged planar surfaces. The angle 806 is 90 degrees, in the depicted example. Therefore, the consecutively arranged planar surfaces are perpendicular to one another.

FIGS. 9 and 10 show another example of a heat exchanger 900 that may be included in the vehicle system 10 shown in FIG. 1. Thus, the heat exchanger 900 may be the heat exchanger 50, shown in FIG. 1, in some examples.

FIG. 9 shows the heat exchanger 900 having a first coolant duct 902, a second coolant duct 904, and a fin structure 906 extending between the coolant ducts. FIG. 10 shows the heat exchanger 900 without the first coolant duct 902, exposing a greater viewable portion of the fin structure 906. As shown, the fin structure 906 is arranged at a non-straight angle 1001 with regard to an axis 1000 parallel to a plurality of the planar surfaces in the fin structure and a general direction 1002 of airflow entering the fin structure. Specifically, the angle 1001 is 15°. However, other angles have been contemplated.

FIG. 11 shows a detailed view of a portion 1100 of the fin structure 906 shown in FIGS. 9 and 10. As illustrated, a leading layer of fins 1102 (e.g., a peripheral layer of fins) is tapered to accommodate for the non-straight orientation (e.g., 15° alignment) of the fin structure. The leading layer of fins includes a plurality of stacked fins. Each of the fins may be similar in size and geometry and are longitudinally and laterally aligned. It will be appreciated that a trailing set of fins may also be tapered to accommodate the non-straight orientation of the fin structure with regard to the orientation of the coolant conduits (902 and 904) shown in FIGS. 9 and 10. Therefore, the leading and trailing layers of fins are tapered and each of the cells in the leading and trailing layers of fins have unequal cell sizes. Specifically, the lateral width of the cells in the set of leading and trailing fins varies in a longitudinal direction. The portion 1100 of the fin structure shown in FIG. 11 also includes a second layer of fins 1104 offset from the leading layer of fins 1102. Additionally, the leading layer of fins 1102 includes a plurality of cells 1106.

In another example, the fin structure may comprise a pyramid type structure including four or five faces with edges comprised of small metal structures such as thin bars or rods. It will be appreciated that a pyramid type structure may also create a desirable amount of turbulent airflow in the heat exchanger. FIG. 13 shows an example pyramid type structure 1300 including a plurality of rods 1302. The rods may have a circular cross-section or an oval cross-section in some examples. The rods 1302 may be coupled to one another to form triangular cells 1304. A portion of the triangular cells 1304 may be orientated in a transverse and longitudinal direction and another portion of the cells may be orientated in a lateral and longitudinal direction. It will be appreciated that the pyramid type structure 1300 may be coupled to coolant conduits. Specifically, the structure 1300 may interpose two coolant conduits.

FIG. 14 shows a method 1400 for operation of a heat exchanger. The method may be implemented via one or more of the heat exchangers disclosed in FIG. 1-13 or may be implemented via another suitable heat exchanger.

At 1402 the method includes flowing coolant through a first coolant duct and a second coolant duct. Next at 1404 the method includes flowing turbulent air through a plurality of repeating offset cell structures formed by a plurality of stacked layers of fins, each fin including a repeated pattern of folds. In one example, the airflow through the plurality of repeating offset cell structures is isotropically turbulent. In another example, the offset cell structures are arranged at a non-straight angle with regard to an outlet direction of a fan.

Note that the example routines included herein can be used with various engine and/or vehicle system configurations. As such, various acts, operations, or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts or functions may be repeatedly performed depending on the particular strategy being used.

It will be appreciated that the configurations and methods disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure. 

1. A heat exchanger comprising: a plurality of stacked layers of fins, each fin including a repeated pattern of folds, the plurality of stacked layers of fins forming a plurality of repeating offset cell structures; a first coolant duct and a second coolant duct coupled to peripheral fins in the plurality of stacked layers of fins; and a fan directing air through the repeating offset cell structures.
 2. The heat exchanger of claim 1, where the airflow through the repeating offset cell structures is isotropically turbulent.
 3. The heat exchanger of claim 1, where the plurality of stacked layers include a first stacked layer having a plurality of fins sequentially stacked and aligned in a transverse direction extending between the first and second coolant duct and a second stacked layer having a plurality of fins sequentially stacked and aligned in the transverse direction, the first stacked layer is offset from the second stacked layer in longitudinal direction.
 4. The heat exchanger of claim 3, where the longitudinal direction extends between the inlets and the outlets of the first and second coolant ducts.
 5. The heat exchanger of claim 1, where each of the fins are identical in size and geometry.
 6. The heat exchanger of claim 1, where each of the fins extend in a longitudinal direction from inlets of the first and second coolant ducts to outlets of the first and second coolant ducts.
 7. The heat exchanger of claim 1, where the stacked layer of fins are angled at 15° with regard to the general direction of airflow generated by the fan.
 8. The heat exchanger of claim 1, where each of the fins are formed of a continuous piece of material.
 9. The heat exchanger of claim 1, where the cell structures have a square cross-section.
 10. The heat exchanger of claim 1, where each of the fins includes a plurality of consecutively arranged planar surfaces.
 11. The heat exchanger of claim 1, where each of the fins includes a plurality of square air-flow channels and where each air-flow channel is bounded by three consecutively arranged planar sides.
 12. The heat exchanger of claim 1, where each of the fins includes a plurality of triangular air-flow channels and where each air-flow channel is bounded by two consecutively arranged planar sides.
 13. A method for heat exchanger operation, comprising: flowing coolant through a first coolant duct and a second coolant duct; and flowing turbulent air through a plurality of repeating offset cell structures formed by a plurality of stacked layers of fins, each fin including a repeated pattern of folds.
 14. The method of claim 13, where the airflow through the plurality of repeating offset cell structures is isotropically turbulent.
 15. The method of claim 13, where the offset cell structures are arranged at a non-straight angle with regard to an outlet direction of a fan.
 16. A heat exchanger for an engine, comprising: a first and second coolant ducts spaced way from one another; a first layer of stacked and transversely aligned fins extending between the first and second coolant ducts, each of the fins included a repeating pattern of folds; and a second layer of stacked and transversely aligned fins extending between the first and second coolant ducts, each of the fins included a repeating pattern of folds and the first layer of fins longitudinally offset from the second layer of fins.
 17. The heat exchanger of claim 16, where a plurality of planar surfaces in peripheral fins in the first and second layer are in face sharing contact with a surface of either the first coolant duct or the second coolant duct.
 18. The heat exchanger of claim 16, where the fins in the first layer and the second layer form a plurality of offset cell structures.
 19. The heat exchanger of claim 16, where a range of ratios between a width and a length of each of the repeating planar surfaces is 1/1-1/15.
 20. The heat exchanger of claim 16, where each of the fin structures includes a plurality of consecutively arranged planar surfaces, each planar surface arranged perpendicular to the subsequent and preceding planar surfaces. 